[Belyaev] and his intern, Lyudmila Trut, wandered around Russia searching for foxes to start their experiment. Foxes were chosen based on their behavior in the presence of humans. Those that showed slightly more tolerance of humans were brought back to their Novosibirsk lab to serve as the start group.

and his intern,
Lyudmila Trut, wandered around Russia searching for foxes to start their
experiment. Foxes were chosen based on their behavior in the presence
of humans. Those that showed slightly more tolerance of humans were
brought back to their Novosibirsk lab to serve as the start group.

and his intern,
Lyudmila Trut, wandered around Russia searching for foxes to start their
experiment. Foxes were chosen based on their behavior in the presence
of humans. Those that showed slightly more tolerance of humans were
brought back to their Novosibirsk lab to serve as the start group.

and his intern,
Lyudmila Trut, wandered around Russia searching for foxes to start their
experiment. Foxes were chosen based on their behavior in the presence
of humans. Those that showed slightly more tolerance of humans were
brought back to their Novosibirsk lab to serve as the start group.

The original foxes were imported
from Canadian fox farms, not chosen from around Russia as this article says. Also, the very first foxes selected for the founding population of the study
were not chosen based on their behavior. A control group was
kept, so the researchers (of which there are more than two) didn’t want
that first set to be more friendly than the average farm fox.

[The changes were] not all on the outside—their adrenal glands became more active, resulting in higher levels of serotonin in their brains, which is known to mute aggressive behavior.

The tame foxes’ adrenal glands became less active, and secreted less cortisol, a hormone which is associated with stress. Additionally, they have been shown to have higher levels of serotonin in their brains (not secreted by their adrenals, however), which is associated with less aggressive behavior, though I think saying that serotonin “mutes” aggressive behavior might be going a bit far. We don’t fully understand the link between serotonin and aggression.

I do like seeing the Farm Fox Experiment covered in the popular press, though. It’s such a great way of explaining how selection works and such a fascinating demonstration of how quickly selection can have an effect!

And it was not all on
the outside—their adrenal glands became more active, resulting in higher
levels of serotonin in their brains, which is known to mute aggressive
behavior.

Dogs evolved from
wolves. We’ve been certain of that for several decades by now. But
there remain a lot of questions: exactly when did dogs first appear?
Did they join their fate with humans when we were hunter-gatherers,
or were they attracted to us after the Agricultural Revolution,
because we had begun to farm? Which group of ancient wolves did they
come from? Knowing more about where dogs began will help us
understand modern dogs and their behavior better. Academics are
currently conducting a very polite debate about these questions in
journals, waged over the course of years.

Grey Wolf

Why is the problem such
a hard one? Until recently, the tools that we were using to get
information about ancient canids were very limited. Our first tool
was archaeology: digging up the remains of ancient canids, trying to
figure out if the animal was more dog-like or more wolf-like, and
then estimating the age of the find. It’s not entirely
straightforward to tell an ancient dog from an ancient wolf using
only bones, especially when many archaeological finds are incomplete.
The important parts of the skeleton for this work are the teeth and
skull: dog muzzles are shorter than wolf muzzles, so that their teeth
are more crowded into the available space, and the last premolar and
first molar are smaller in dogs than in wolves. Some interesting
finds have suggested that dog-like canids first appeared between
15,000-30,0000 years ago — that’s just before agriculture was
first developed.

A well publicized 1997
paper from Vilà et al. popularized a new tool for dating dog
domestication: analysis of mitochondrial DNA, or mtDNA. Mitochondrial
DNA is the DNA inside the mitochochondria in our cells. Mitochondria
used to be free-living organisms; they began to live symbiotically in
the cells of multi-cellular organisms billions of years ago, but
still have their own separate DNA. Mitochondrial DNA gains new
mutations at a regular rate, and this can be used as a molecular
clock: compare the mtDNA of two different species, and by counting
the differences, you can estimate how many years ago the ancestral
species split into the two new species.

The problem is that
this molecular clock isn’t very reliable or very precise: we don’t
really know exactly how fast mtDNA mutates, which makes the clock
hard to calibrate. The 1997 findings suggested that dogs and wolves
separated about 130,000 years ago — an order of magnitude more than
the archaeological estimates suggested! Other mtDNA studies have been
conducted since then, with a variety of results, none of them
conclusive. It turns out that dog and wolf mtDNA divergence is
particularly difficult to analyze because dogs and wolves can and do
still interbreed. My golden retriever may not have a wolf in his
immediate ancestry, but I suspect you don’t have to go back all
that many thousands of years to find one — certainly not all the
way back to the domestication split. And there are quite a few
populations of dogs in the world with much more recent wolf ancestry
than that. This interbreeding really screws up the molecular clock.

In the last few years,
though, the revolution in genomic tools — cheap and efficient
sequencing of complete genomes — has gotten to the point where it’s
affordable to completely sequence the genomes of a number of dogs and
wolves for a study. This is significantly changing the kinds of
things we can learn about how dogs and wolves genetically differ.
Instead of guessing at changes in mtDNA, we can look at the actual
genes that differ between the two species. These new studies have set
the date of dog domestication at 11,000-32,000 years ago, a date
which is similar enough to the archaeological findings to make a lot
of sense.

We’ve learned a lot
of interesting things from these new sequencing studies beyond just a
more precise date of domestication. A little more than a year ago,
Axelsson et al. found that dogs make more of an enzyme for digesting
starch than wolves do. The enzyme is called amylase, and dogs have
multiple copies of the gene, whereas wolves have only one. These
researchers wondered if this improved ability to digest starch meant
that dogs were domesticated after the appearance of agriculture —
if starch digestion was part of the domestication process. However, a
study published in January 2014 by Freedman et al. dug deeper into
the amylase question and discovered that in fact, not all dogs have
extra amylase genes. Some ancient breeds, like the husky, do not.
Neither does the dingo. These very recent findings suggest that dogs
were in fact domesticated before the Agricultural Revolution, and
that some breeds later developed an improved ability to eat what we
eat, adapting to their new post-domestication diet. You might imagine
that such a change would have been less important to the husky,
living in the cold north as it did, where meat was on offer much more
often than plants.

Freedman et al. also
suggested that dogs didn’t actually evolve from wolves. Wait,
what? It's possible that both dogs and wolves evolved from a
different ancient canid which doesn’t exist any more. Freedman came
to this conclusion using a somewhat complicated genomic analysis
which doesn’t tell us anything about what such a canid would have
been like, but it’s an idea which resonates with reservations I’ve
always had about the “dogs came from wolves” theory. Wolves are
so shy, so hesitant to come near humans, and so focused on making
their living by hunting. The ancestors of dogs seem more likely to
have been scavengers, willing to live close to humans. Maybe some
ancient canid did give rise to both species — the one moving closer
to human civilization and becoming dogs, the other farther away and
becoming wolves. With several studies coming out every year about dog
domestication, we may learn more very soon.

About the Dog Zombie

Jessica Perry Hekman, DVM, PhD is fascinated by dog brains. She is a postdoctoral associate at the Broad Institute of MIT and Harvard, where she studies the genetics of dog behavior. Her interests include the stress response in mammals, canine behavior, canine domestication, shelter medicine, animal welfare, and open access publishing. You may learn more about Jessica at www.dogzombie.com, or email her at jph at dogzombie dot com. All opinions expressed here are her own.

For the animal shall not be measured by man… They are not brethren, they are not underlings: they are other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendor and travail of the earth. (Henry Beston)